Protective or decorative coatings are applied to many different substrates, for example, textiles, paper, wood, leather, glass, ceramics, porcelain, metal, plastics, stone, concrete, and asphalt. Coatings may provide protection of the substrate from corrosion, oxidative aging, mechanical damage, or weathering. For application outdoors or in humid environments, it is generally desirable to utilize polymeric coatings with low water uptake. Water uptake by the coating can lead to plasticization or hydrolysis reactions of the polymer coating with resultant degradation of useful properties such as toughness, weatherability, and abrasion resistance. In addition, water uptake by a coating can lead to accelerated corrosion of a corrosion sensitive substrate as well as loss of adhesion of the coating to the substrate.
Pavement markings are examples of coatings which are subject to wear and must withstand severe use. They are installed on roads to delineate and to provide guidance, warning, and regulatory information to motorists and pedestrians. Important characteristics of pavement markings are low water uptake, durability, reasonable cost, ease in method of installation, handling and installation safety, and visibility.
Other utilities where materials are exposed to conditions of variable humidity include protective coatings on motor vehicles, and coatings on many substrates such as leather, wood, ceramics, textiles, or glass that can benefit from resistance to water uptake.
For environmental reasons and to meet EPA requirements regarding the amount of volatile organic compounds (VOCs) allowable in coating materials, it is highly desirable to apply coatings from water rather than from organic solvents. There has been a continuing search for waterborne materials which produce coatings with reduced water uptake.